Caption: Henry Cavendish (1731-1810), British physicist and chemist. Cavendish was born wealthy and was given a good education. He spent four years at Cambridge and a year in Paris before moving finally to London. His work in chemistry was most important; he showed that gases could be weighed, that air is a mixture and that water is not an element. In physics he showed that the Earth's density was 5.5 times that of water and worked on gravitation. He also studied electricity and heat, proposing that heat comes from "internal motion of the particles of bodies". Much of his physics was unpublished, unknown until the 1870s, and thus not as influential as it could have been.